siemens piezo injectors

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siemens piezo injectors

Postby bwscott » Thu Oct 22, 2009 4:42 pm

HELP! CAN ANYONE TELL ME HOW TO SCOPE PEUGEOT HDI SIEMENS PIEZO INJECTORS AT CRANKING, :oops:
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Re: siemens piezo injectors

Postby Matt Fanslow » Thu Oct 22, 2009 9:37 pm

I'm not sure I understand your issue.

Have you tried scoping them previously and are not content with the patterns captured?

Are you scoping to learn or to diagnose, in other words: Is this car broke?

Are you looking to scope voltage or current?

All the piezo's I've seen are switched both on power and control sides and you will most likely wish to be on both sides. Ground both channels to the driver module's ground or to battery ground and then probe each ckt as you would any other high voltage fuel injector ckt (GDI or Diesel).

Later, Matt.
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Re: siemens piezo injectors

Postby Dave Hill » Sat Jan 09, 2010 8:36 pm

The following capture was taken with the ground reference on the "Other" injector wire, as opposed to battery or chassis ground. The waveform makes more sense taken that way.

Image

HTH

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Re: siemens piezo injectors

Postby Autonerdz » Sun Jan 10, 2010 4:43 pm

Hi Dave,

Just wanted to tell you a better and safer way to do this. You are always taking a risk when you place the scope ground on a voltage source. Besides being at risk for creating a ground loop, you can risk damage from high voltages. This is especially true when working with injectors that may have a high voltage kick. Even with attenuators in place, they don’t function as intended when the scope is not grounded.

Here is the safe way to do it:

Use two channels, both grounded to bat neg. One on each side of the injector. Now deploy a math channel like A-B. The math channel will display what you want (injector voltage drop) and you will still have two more channels you can use safely ;-)

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Re: siemens piezo injectors

Postby Rod_au » Sat Jan 16, 2010 9:16 am

Here is the safe way to do it:

Use two channels, both grounded to bat neg. One on each side of the injector. Now deploy a math channel like A-B. The math channel will display what you want (injector voltage drop) and you will still have two more channels you can use safely ;-)


Thanks Tom. Very Good Tip!!
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Re: siemens piezo injectors

Postby Dave Hill » Tue Feb 02, 2010 10:33 pm

Thanks Tom for the Tip.

I agree that there is some inherent risk with the method I suggested, mainly due to the "ground loop" as you call it. When deploying multi channels, it is vital to consider where the ground connection is made & what it is shared with.

However, for the purpose of the capture I displayed, I don't think that my method is unsafe.

Although I am always open to correction.

Cheers Tom

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Re: siemens piezo injectors

Postby mapengo » Mon Feb 15, 2010 8:09 pm

Hi All,

Tom, is there any chance you can post a capture using the method you recommend, maybe with the "risky" method on the other 2 channels for comparison?

I am having a hard time visualising it.

Cheers

Doc...
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Re: siemens piezo injectors

Postby Autonerdz » Mon Feb 15, 2010 9:39 pm

Mapengo,

The short answer is no thank you. :?

It would not be wise to do it the 'unsafe' way, especially when there is a high voltage kick. As I mentioned, the attenuator needs to be grounded to do its job and protect the scope and allow you to scale the high voltage.

When you have the scope ground on a voltage supply, you cannot ground the scope.

Therefore it would be impossible to show the safe method on two channels and the unsafe method on the other two since the scope must be grounded.

Frankly, I would not want to look at anything with a high voltage kick and have the scope ground attached to the device rather than ground. This puts the scope and the PC at risk of high voltage kick.

You can get away with doing that with low voltage stuff using one channel only. One example might be placing signal and ground for one channel across a floating ground VRS crank sensor, such as on a Ford EDIS system, so you can measure true peak to peak amplitude. With math channels though, it's really not necessary.

Bottom line.....Unless you are really confident in what you are doing, never place the scope ground on a voltage source.

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Re: siemens piezo injectors

Postby mapengo » Tue Feb 16, 2010 7:17 am

Hi Tom,

To be honest, I didn't expect you to risk blowing your scope, it was a bit "tongue in cheek"

I am interested in using the math channel as this is an area I haven't really explored yet, will have a look around to see what info there is on this.

Cheers

Doc...
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Re: siemens piezo injectors

Postby Autonerdz » Tue Feb 16, 2010 6:22 pm

Mapengo,

Here are some images of a negatively controlled gasoline injector form a Toyota done different ways. I was using a 4423 scope so could do this without the need for an attenuator and with no risk to the scope.

This should help you visualize.
Attachments
across2.gif
Channel input and ground across the injector. Input on supply and ground on drive side.
(51.7 KiB) Downloaded 27 times
across1.gif
Channel input and ground across the injecor. Input on drive side ground on supply.
(51.31 KiB) Downloaded 27 times
standard.gif
Standard hook up with scope grounded and channel input on injector drive side.
(52.7 KiB) Downloaded 27 times
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